Field of the Invention and Related Art Statement
This invention relates to an objective part replaceable endoscope tip. The objective part is provided with an objective optical system in which the focus is adjustable by a rotating operation. The objective part of a fixed focus system can be selectively removably fitted.
Generally, in an endoscope, an objective part, in which an objective optical system is formed, and a soft part, forming a flexible insertable part, are integral. However, there is also an endoscope in which the objective part has a replaceable structures. In the endoscope having a replaceable objective part, objective parts of the three below mentioned types are selectively fitted:
(1) An objective part in which the focus is adjustable by rotating a focus ring by hand.
(2) An objective part to the tip of which a hood or a visual field converting adapter, which converts a visual field angle and visual field direction, can be removably fitted. (This objective part may be either a fixed focus system or an adjustable focus system.)
(3) An objective part of a fixed focus to the tip of which a visual field converting adapter, which converts a visual field angle and visual field direction, can not be removably fitted.
The prior art examples relating to the objective parts of the above mentioned three types are Japanese utility models laid open Nos. 158203/1981, 87704/1982, 59114/1985 and 59215/1985 by the present applicant.
The above mentioned prior art examples, which are frequently removably fitted, have been connected with a soft part by a rotary engagement of a screw mount by which they can be easily removably fitted.
However, one defect in the above mentioned type (1), is that at the time of the focus adjusting operation by rotating the objective part, torque will be applied to the screw mount part of the objective part, and thus the connection with the soft part will loosen. One defect in the above mentioned type (2), is that when the hood or visual field converting adapter, connected to the objective part, is to be disconnected, the connection will also loosen.